Pen



FIG. 1 is a right side elevational view of a pen showing my new design, the left side being a mirror image thereof;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a top plan view thereof; and,

FIG. 5 is a bottom plan view thereof. 

The ornamental design for a pen, as shown and described. 